I'm still at it too. I can stretch it out to as many as four weeks - before they just about grow off the end of my fingers! Counting a nice tip I pay about $9 US.

My own nails are pretty damn hard - but not unbreakable. I'e been covering thumb plus index and middle fingers for almost 7 years now.
I also use my fourth finger regularly but I almost never break tha one - and it's the easiest to work around if it's not in full working order.

One disadvantage though; when you bang 'em in a such a way as they used to break - IT HURTS LIKE HELL! Not only that, but it doesn't stop hurting for a long time! Oh well, I guess pain is better then a broken nail!